Many mobile web sites and apps work with ad networks that deliver, manage, and target the ads you see. They may do this to understand how many users saw an ad, to learn which ads are effective in getting users to purchase a product or download another app, and to keep track of user activity in order to tailor the ads they show on other web sites or apps. They may also link other data they can obtain, on or offline, to enhance the profile they have created about the user of a device.

Some mobile web browsers support the use of third party cookies (often set by an ad network) to enable this tracking. Cookie control settings in the mobile browser allow a user to clear this information. Some ad networks will also provide users with the ability to set an opt-out cookie that tells the ad network not to target the ads they show based on web surfing information. (Beware – clearing all the cookies from your browser will clear the opt-out cookie, so you must manually re-set your opt-out cookies every time they are cleared.)

Generally, apps do not provide ad networks with the ability to set a cookie to track users. Instead, ad networks that track users of apps may use another identifier available on your device. This can be done with a “device identifier,” a MAC address, with a special identifier stored on the “pasteboard,” or by a method known as device fingerprinting.

To opt-out of targeting that relies on the device identifier, a user needs to therefore provide the ad network with this identifier to be kept on a “do not target” list of sorts. We provide this page to offer users one place where they can find links to a range of mobile opt-out options. Since each company may handle its “opt-out” process differently, we urge users to read the information that each company provides.